My Quora answer.
There is indeed an Alt Left movement but as John Doe alludes to below, it is quite small. In fact, it is much smaller than the Alt Right. The Alt Left could possibly be seen as “the left wing of the Alt Right.” The original Alt Leftists were Leftists and progressives on the Alt Right who felt very uncomfortable and out of place there for many reasons, mostly because in many ways, these people are Leftwingers, despite their presence on the Alt Right. They finally broke away from the Alt Right and formed an Alt Left.
The Alt Left has been described in many ways. “It’s the Alt Right, except they like Mao more than they like Hitler,” is not a bad description. Other descriptions are the place where Pat Buchanan meets Ralph Nader, the place where Mussolini was when he abandoned Marxism and before he adopted fascism. The Alt Left is where the Left and Right meet at the bottom of the circle if you envision politics as circular instead of linear.
Most Alt Lefties supported Bernie Sanders, but Sanders would probably not like the Alt Left much. Now most of them will vote for Hillary even though they hate her. A few are voting for Trump.
The Alt Left has all sorts of wings but some commonalities seem to be a negative view of the Cultural Left ranging from annoyance to contempt alongside explicitly leftwing economics. So they are Left on economics, but somewhat Right on culture.
Really though the Alt Left is to the right of the Cultural Left who they think has gone too far but they are to the left of the Social Conservatives who they think are crazy. A good way to look at them might be to think of the Left as it was from WW2 until the 1960’s Counterculture – the Old Left. They are conservative Leftists, sort of like how a lot of the Communist countries used to be.
Here are two posts, one a post and one a site, from some of the earliest Alt Leftists. The first is a manifesto and the second is one of the biggest Alt Left websites. There are also some Alt Left groups on Facebook now.
Dealbreakers: What the Alternative Left Is Not
My Quora answer.